<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>表格样式</title>
    <style>
        table{
            border: 1px dashed red;

            
        }
        td,th{
            border: 1px solid #999;
        }


    </style>
</head>

<body>
    <table border="1" width="500px" height="500px" cellspacing="5">
        <tr>
            <th>序号</th>
            <th>学生姓名</th>
            <th>年龄</th>
        </tr>
        <tr>
            <td>1001</td>
            <td>tom</td>
            <td>23</td>
        </tr>
        <tr>
            <td>1001</td>
            <td>tom</td>
            <td>23</td>
        </tr>
    </table>

</body>

</html>